ZAP

As seen on YouTube - The Spectrum LEARNING BASIC

How to create a Laser beam using the PLOT and DRAW commands. 

ZAP 

Protect the red planet and zap as many Aliens as possible!!!  When shield falls beyond half way mark zap cyan boss, or the Aliens above the boss to gain a re-charge on shield.

FUSE emulator - To prevent continuous firing set inputs to Kempston, tick Kempston joystick interface and then reboot and upload game.